A rare meteorite crash site has been discovered in Inver Grove Heights – the first site found in Minnesota – and researchers hope it will soon be added to the map of other known impact sites around the world.
“I look at rock samples all day, and I’ve never seen anything like this before,” said Julia Steenberg, a geologist and research scientist at the University of Minnesota. “It’s kind of like a breath of fresh air to find and discover something new.”
There are about 190 confirmed locations worldwide, including about 30 in the United States.
“We are obsessed with geology and it really gets us excited,” said Tony Runkle. Principal geologist at the Minnesota Geological Survey, who said the site is “definitely” one of the most interesting discoveries in the 33 years of the survey.
The crater below Inver Grove Heights is about 2.5 miles wide and can span an area of 9 square miles in total. Steinberg, who grew up in Dakota County, said it dates back about 490 million years.
The crater itself is hidden several hundred feet underground under sediment, she said, not visible to the human eye.
Scientists at the Minnesota Geological Survey, the research arm of the U’s College of Earth and Environmental Sciences, found the site of a meteorite impact in early 2021 as they updated geologic maps of Dakota. Steinberg said they named it the Pine Bend Impact, after the Inver Grove Heights area where it was found.
Beneath most of the state’s soil are flat layers of glacial sediment. Beneath the glacial layers are sandstone, limestone, and shale. While the scientists worked at Inver Grove Heights, they saw that the layers, which are usually stacked in a predictable pattern, were out of order and certain layers appeared to have flipped.
“The more I looked at the records in that area, it just didn’t make any sense,” Steenberg said.
She recalled locating tiny, cracked grains of sand known as shock quartz – a common determinant of a meteorite impact. The granules consist only of the massive shock and pressure from a meteorite impact or a nuclear explosion, she said.
Most of the time, Steenberg said, meteorites burn before they hit Earth — but sometimes collisions occur.
“There is intense pressure associated with it… which produces immediate geological effects,” she said.
To verify, Steenberg sent photos and samples of the sediment to the Museum of Natural History in Vienna, Austria, and the Institute of Geosciences at the University of Brazil. They asserted that, in fact, quartz was shocked.
Steinberg said researchers are learning about the site and want to know the exact size of the meteorite, adding that U hopes to secure funding for the work. She added that they plan to publish their findings and maps soon.
Since the site is newly discovered, it is not yet included in the official Earth Impact DatabaseAlthough researchers hope it will be added, she said.
In the upper Midwest, impact sites have been found in Wisconsin, North Dakota, and Iowa. Rock Elm Crater in western Wisconsin, about halfway between the Twin Cities and Eau Claire, is the closest known crater to Minnesota. It has a diameter of about 3.7 miles, which is slightly smaller than the Pine Bend Impact, Steinberg said
Amy Luz, a spokeswoman for Inver Grove Heights, said residents are excited to see the Pine Bend monument as part of the city’s history.
“We are delighted, intrigued and relieved to discover Mrs. Steinberg,” Luz said in an email. “It’s so pleased [we] It could become an important geological site, intriguing that the discovery could give scientists more data they need to predict future meteorite impacts on Earth and mitigate the lack of any statistical chance of another meteorite hitting our city. “
“Infuriatingly humble analyst. Bacon maven. Proud food specialist. Certified reader. Avid writer. Zombie advocate. Incurable problem solver.”
